Goldman Sachs just bought a one-person startup, and it's betting it could change the day-to-day lives of its bankers (GS)Goldman Sachs has bought a one-person startup to help supercharge its bankers' financial modeling skills.The bank is hoping the cloud-based software can begin to do for investment banking what SecDB, its risk-management system, has done for the securities division by creating a single place where models can be stored and analyzed. Goldman Sachs has been searching for years for an investment-banking equivalent to the vaunted risk-management system its traders use. It may have just found i...